Oscillation system



July 26, 1938. R. H. SEAMAN ET AL 2,124,595

OSCILLATION SYSTEM Filed May 18, 1936 k 2 sheets-sheet 1 i v .L /0 18 T 6 8 24 D Y r15. C7. 3

Richard h. Seaman,

Car/ A. fchwenden,

July 26, 1938. R. SEAMAN ET AL 2,124,595 v OSCILLA'IION SYSTEM Filed May l8, 193 6 2 Sheets-Sheet 2 Ema/whom Ric/70rd H. Sea/mm,

Car/ A. Schwenden,

Patented J uly 26, 1938 UNITED STATES PATENT OFFICE OSCILLATION SYSTEM Application May 18, 1936, Serial No. 80,462

10 Claims.

Our invention relates broadly to electron tube oscillator systems and more particularly to a novel type of electron tube oscillator characterized by the condition wherein the filament cathode has a higher dynamic potential than the plate element in the electron tube.

One of the objects of our invention is to provide a type of electron tube oscillating system in which the tube oscillations are Very persistent.

Another object of our invention is to provide a circuit network connected in such a way to a thermionic tube as to have the plate element in the tube dynamically at a low potential and the hot cathode at a higher potential.

A further object of our invention is to provide means for connecting the plate, the grid, and the filament of a thermionic tube to selected portions of associated circuit elements whereby the circuit is maintained in a state of oscillation,

even though the load condition is changed over a wide range.

Still another object of our invention is to provide means for connecting a thermionic tube 5 in such relation to associated circuit elements as to obtain a frequency of oscillation considerably higher than that which would be obtained if customary tube circuitswere employed.

A further object of our invention is to provide an arrangement of inductive and capacitive elements in an oscillatory circuit embodying an electron tube, whereby the filament element in the tube may be connected in the dynamic, oscillating circuit at a potential higher than the dynamic potential on the plate element in the tube; the filament being energized by a dynamically balanced, separate source of power.

Still another object of our invention is to provide a push-pull arrangement in an oscillatory 40 circuit operating in accordance with the fundamental characteristics of our invention.

A still further object of our invention is to provide a cascade arrangement of an oscillator tube and an amplifier tube, in which the filament element in each tube is maintained dynamically at a higher potential than the respective plate element.

Other and further objects of our invention reside in the elements and circuit arrangements hereinafter more fully described, with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of the oscillator circuit of our invention; Fig. 2 shows a modification of the arrangement indicated in. Fig. l, and is especially suitable for very high frequency work; Fig. 3 is a schematic diagram of a push-pull arrangement of the oscillator system of our invention; Fig. 4 shows a pushpull arrangement of modified form more suitable for high frequency work; Fig. 5 is a schematic diagram of an arrangement which is more powerful, and more adaptable to very high frequency Work; and Fig. 6 is a schematic diagram of a circuit utilizing two tubes in cascade in order to obtain increased power out-put from the oscillator.

Referring to Fig. 1, reference character I denotes a customary three-element tube having a filament 2, grid 3, and plate 4. Reference character l5 denotes a grid leak resistance, and M a grid condenser, the combination providing a bias potential'for the grid 3. Reference characters l2 and' I3 denote high frequency by-pass condensers. A B battery for supplying power in the plate circuit is indicated at H. Reference character l6 denotes a ground. A tuning condenser by means of which the frequency of the oscillating system can be adjusted to desired values is indicated at 9. The most significant feature of the circuit arrangement consists of the coils 5 and 6, which are exactly alike and wound together as a single coil. They are shown separately only in order to avoid confusion in circuit connections. As the condensers [2 by-.

pass high frequency currents, the coils 5 and 6 may be considered, as far as high frequency currents are concerned, as being, in effect only one coil. The by-pass condensers l2 have the purpose of avoiding a short circuit on the A battery 10 supplying the power to the filament 2. If the battery 10 is replaced by the output of a low frequency source for supplying the filament power, by-pass condensers 12 must be chosen such as to form an open circuit to the low frequency power supply. Contacts 1 and 8 v on coils 5 and 6, respectively, connect to the 7 ends of the filament 2.

In the circuit of Fig. 1, as in all the circuits illustrated, the dynamic oscillating circuit includes the circuit from the grid to the parallel radio frequency paths comprising the twin coils 5 and 6 and the by-pass condensers l2, the connections to the filament from the twin coils, and the plate circuit through thecondenser l3, as well as the interelectrode paths within the tube. The sources of power Ill and H do notenter substantially into dynamic oscillatory circuits but supply the power and the static potentials to the filament and plate elements.

.. Thus, as far as dynamic oscillations are ,con-

cerned, plate 4 is at the lowest potential while the filament is at a high potential. This is an essential dilference between customary tube circuits and the circuit of our invention. With contact 1 at point 31' in the circuit, the corresponding end of the filament would be at a low dynamic potential, while if contact 1 was connected at the point 36, the corresponding end of the filament would be at the highest available dynamic potential with respect to the, potential on the plate 4. It will be noted that with the connection shown, the grid and filament both are dynamically at a high potential with respect to the plate. 1 a

As mentioned before, coils 5 and 6 are wound the case asis evident from the explanation just given. In our experiments we have found the.

following-great advantages in the oscillator system of-our invention: The circuit oscillations are verypersistent, that is, the circuit practically will not stop from oscillating no matter how it is loaded or adjusted as to frequency, and the like.

We have also discovered that the frequency of.

oscillation is considerably'higher than with customary types of oscillators. In our experiments we' haveset up, for instance, a circuit as shown in Fig. 1, and a Hartley oscillator circuit in which actually only one coil is used across the variable condenser, and in which the" plate is dynamically at a high potential with respect to the filament.

The condenser was exactly the same in both circuits, and the plate-grid coil in the Hartley circult was identically the same as our combined coi1'5, 6, shown in Fig. 1. The result wasthat theiI-Iartley oscillator generated frequencies corresponding to a wave length of about 20 meters, while our circuit shown in Fig. 1 generated a frequency .correspondingto a wave length in the neighborhood of about 9 meters. Hence, we can see that with such a network, we have great advantages in the ultra-high frequency band over customary oscillators, in addition to the advantage that more persistent oscillations, with more..power,.can be produced. ."Fig. 2 is a. modification of the circuit shown in Fig. 1. .We have omitted the variable condenser 9 shown in Fig. 1 which connects essentially across the grid and the plate and. serves the pur pose of decreasing and adjusting the frequency of the generated oscillations. With this condenser 9 omitted in Fig. 2 powerful oscillations at ultra-high frequencies can be produced which areconsiderably higher in frequency than oscillations produced in customary tube' oscillators. It will be noted that a .C battery I! replaces the automatic grid bias provided by condenser 14 and resistance 15 of Fig.1. In Fig. 2, reference characters 5 and 6 denote again' the two coils which are'wound closely together and separated at the respective ends, for direct current supply, by means of the high frequency by-pass condensers 12. Contact points 1 and 8 again serve the purpose of'supplying a suitable high dynamic potential to the respective filament ends, with respect to. the low dynamic potential of the plate 4. The grid 3 is again, dynamically at a high potential, while the filament 2 also is relatively at a high dynamicfpotential with respect to the potential of the'plate' 4. Reference character I6 again denotes a ground which is connected to the plate terminus of the coil 5.

shown in Fig. 1. The electron tube l contains a filament 2, a grid 3, and a plate 4, as in Fig. 1. The grid-plate condenser 9", is variable for the sake of adjusting the frequency of the generated oscillations. For very high frequency work, this condenser may be omitted. Reference characters 5 and 6 denote the characteristic duplex coil of our invention, and it will be noted that the end 35 of coil 5 is disconnected from the remainder of the circuit. Coils 5 and '6 are again wound closely together and are exactly alike. Contact points I and 8 are connected at suitable points on coils 5 and B, respectively, in order to provide --the corresponding filament with a potential dynamically at a higher level than the low dynamic potential of the plate 4. A condenser for bypassing high frequency currents is represented at l3, and reference characters and II designate the A and B batteries respectively. It will be noticed that neither an automatic nor a battery source of grid bias is employed. We have found that with such a network as in Fig. 5, most persistent and powerful oscillations are obtained.

Fig. 3 gives a push-pull arrangement of our new type of oscillator. Reference characters and 6 indicate thetwin coils which are wound closely together. High frequency by-pass condensers are shown at I2 and I3, and reference character l6 denotes a ground, as in Figs. 1 and 2, the ground 16 in Fig. 3 being connected at the middle of coil 5. The automatic grid biasis provided, as in Fig. 1, by means of a grid leak resistance I5 and a grid condenser M, for the grid 2| in tube I 8, and by resistance l5 and condenser l4 for the grid 2! in tube l9. The variable condenser 9 across the respective grids of tubes, l8 and 19 serves again the purpose of adjusting to a desired frequency. Condenser 9 maybe omitted for very high frequency work. The filaments Hand 20 of tubes l8 and I9, respectively, are energized by means of a single source, Ill; and the source I l supplies the power to the plate branches of tubes l8 and I9 which includes the plate elements 22 and'22', respectively. Both power sup plies IE3 and II can be contained in a customary power pack; or source II can be replaced by a B eliminator, and sourcev Ill by the secondary of v low frequency currents, but essentially a short circuit for the generated high frequency current.

- Contacts 1 and 8, which connect to filament 20, as well as contacts 23 and 24, which connect with filament 20, are adjusted to suitable'points along the twin coils 5 and 6 so that the respective filaments .28 and 2B of the two push-pull tubes 18 and 19 are dynamically at a high potential with respect to the low potential of the respective plates 22 and 22' of tubes I8 and Hi. It will be noted also that the two grids 2i and 2i are dynamically at a high potential. Pushpull oscillators of this type combine all the features and advantages brought out in connection with the explanation of Fig. 1, in additionto the features inherent to all pushpull oscillatorsthe latter being very well known in the art. r

Examining the circuit arrangement of Fig. 3 closer, will bring out the essential difference between customary tube oscillators and the novel oscillator of our invention. We note, for instance, that theplates are connected together,

that means,-that theyare dynamically as Well as statically one unit while the filaments are dynamically two separate essential elements. They. have, in our novel type of oscillator, functions like the plates in customary tube oscillators, because the filaments in our novel type of oscillator are dynamically at a high potential. The two grids also have to be separate, because they too are dynamically at high potentials.

Inasmuch as the oscillator of our invention, according to the explanation just given, has inverse actions in comparison to standard tube oscillators, a modified push -pull circuit arrangement employing a single tube of unique description has been devised and is shown in Fig. 4. The single tube 25 embodies two filaments 26 and 21, two grids 28 and 29, and only one p1ate3Il, and will produce customary push-pull actions. For the sake of simplicity'and clearness, we have shown direct current power supplies in Fig. 4. Reference character II] denotes the source of power for the filaments 25 and 21, which are connected through contacts I and 8, and 23 and 24, respectively. The source for the plate supply is shown at, and separate sources for producing desired grid biases are indicated at 3I and 3|. Condensers I2 and I3 operate to bypass high frequency currents. The twin coils 5 and 6 are exactly alike, as before, and are wound closely together. i

The contacts 1 and 23, and 8' and 24, connected along the respective coils 5 and 6, are adjusted so that the corresponding filament potentials are higher than the low dynamic potential on plate 39. The dynamic potential on plate 39 is sup:

plied through the tap 38 on coil 5, tap 38 being held at ground potential by connection to the ground IS. A variable condenser can be connected between the two grids 28 and'29 in order to decrease and adjust the oscillator frequency. With such an arrangement as that shown in Fig. 4, most persistent oscillations at a greatly increased frequency can be produced.

Fig. 6 shows another novel arrangement of our invention wherein an additional tube 32 is employed as an amplifier in cascade with the oscillator tube I. For the sake of simplicity, tube I with the filament 2, grid'3, and plate 4, and tube 32, with the filament 33, grid 34, and plate 35, are customary three-element tubes. Condensers I4 and I4 and resistors I5 and I5" supply, in the particular circuit shown, the proper bias potentials for the grids 3 and 34. These potentials can, of course, also be produced with customary C batteries. The grid condenser I 4 and grid leak resistance I5 of tube I may be omitted in order to produce the effects brought out in connection with the explanations of Fig. 5.

Fig. 6 shows the twin coils 5 and 6, which are exactly alike and wound closely together, connected in circuit with tube I. An additional pair of coils 39 and 40, which are also exactly alike and wound closely together, is employed in connection with tube 32. Coil 4|, inductively coupled with coils 39 and 40, is the output coil of the oscillator system. Condensers I2 and I3, as usual, are connected as high frequency bypass condensers and additional by-pass condensers I2 are employed in connection with the twin coils 39 and 40. Battery I supplies the power to the respective filaments 2 and 33, and source II supplies the power to the circuit connected in common to plate 4 and plate 35. Contacts I and 8 on coils and 6, respectively, as

It will be noted that the filament 2, by means of contacts 'I' and 8 on the twin coils 5 and 6, is'aga'in dynamically at a high potential with respect to the dynamic potential of plate 4, while the grid' 3 alsois dynamically at a high potential.- Thatfis, the tube oscillator utilizing tube I'has essentially the featuresbrought out in connection with Fig. 1'. The amplifier arrange ment shown in Fig. 6 to the right of tube I and utilizing tube 32, also has the filament dynamically at a comparatively high potential, since contacts 43 and 44 are set close to the right hand or highdynamic potential ends of the corresponding twin coils 39.and 49. The grid 34 of tube 32 is energized through contact 42 from a suitable point along coil 5 in the actual tube oscillator" circuit. The contact 42 could also be connected at places along coil 6, since dynamicallybothcoils are in multiple and act together." With the arrangement shown in Fig. 6, we can obtain greatly increased power output of ve'ry'persistent oscillations, and increased frequencies of oscillation.

It will be understood that the oscillating systems herein disclosed are typical of many 'dif-' ferent circuits, inwhi ch electron tubes'can be employed in such a way as'to have the. plate dynamically at lower potential than the hot cathode as well as the grid. Itis'not intended,

therefore,- that our invention be limited to the particular embodiments shown, but only as defined in the accompanying claims. I NVhatwe claim'asnew and desire to secure by Letters Patent of the UnitedStates is as follows:

1. An electron tube oscillating circuit comprising an electron tube having plate, grid and filament electrodes, means for supplying a static potential to said plate electrode, parallel radio frequency paths connected between the plate and grid electrodes and constituted by a pair of in ductances in intimate inductive relation, corresponding ends of said inductances being connected through radio frequency by-pass condensers, a source of filament current connected with said inductances, and means for connecting the terminals of said filament to selected corresponding points on said inductances intermediate the ends thereof, whereby said filament dynamically has a higher potential than said plate and a lower potential than said grid.

2. A push-pull electron tube oscillator system comprising a pair of three-electrode electron tubes and balanced circuits inter-connecting the electrodes of the respective tubes, plate, grid, and. filament elements in each of said tubes, means for maintaining the plate elements in both said tubes dynamically at a low potential, means for maintaining the filament elements in said tubes dynamically at high potentials with respect to the corresponding plate elements, and means connected between the grid elements in said tubes for providing balanced radio frequency excitation for said grid elements, the dynamic potentials for said plate and filament elements'besaid source being connected with one of said in ing obtained by contact with the last said means intermediate the connections'to said grid elements.

3. A push-pull electron tube oscillator system comprising an electron tube having a single plate element, a pair of filament elements and a grid element associated with each of said filament elements, means for maintaining said plate element dynamically at a low potential, means connected between said grid elements for providing balancedradio frequency excitation for said grid elements, said plate element being connected at the dynamic mid-point of said last mentioned means, said filament elements being connected to said last mentioned means on either side of said mid-point connection, both terminals of each of said filament elements being given the same dynamic potential, whereby the filament elements'are maintained dynamically at a higher potential than said plate element.

4. Anelectron'tube oscillating circuit comprising an electron tube having plate, grid and filament electrodes, means for supplying a static potential to said plate element, separate inductance elements disposed in circuit between the plate and the grid electrodes to the opposite terminals of said filament electrode, and a source of filament current connected with said filament electrode through=portions of said inductances, said source being connected with one of said inductances at the connection thereof with said plate electrode and with the other of said inductances at the end remote from the connection thereof to said grid'electrode, said inductances being arranged in intimate inductive replate and the grid electrodes to the opposite terminals of said filament electrode, and a source of filament current'connected with said filament electrode through portions of said inductances,

ductances at the connection thereof with said plate electrode and with the other of said in-. ductances at the end remote from the connection thereof to said grid electrode, said inductances being arranged in intimate inductive relation and having distributed capacity effective therebetween to provide substantially a single path for high frequency oscillatory currents, said inductances thereby being operative as a single inductance in the generation of oscillation in said circuit.

6. An electron tube oscillating circuit as set forth in claim 1 and having a variable capacity element connected across said inductances for varying the frequency of the generated oscillations.

7. An electron tube oscillating circuit as set forth in claim 5 and having a variable capacity element connected between the grid and plate elements of said tube for varying the frequency of the generated oscillations.

8. An electron tube oscillating circuit as 'set forth in claim 1 and having means for supplying a bias potential for said grid element.

9. A push-pull electron tube oscillator system between corresponding ends of said inductances;

a center-tap connection to one of said inductances providing the low dynamic potentialfor said plates, and connections to both said inductances at selected points providing the dynamic potentials for said filaments.

10. A push-pull electron tube oscillator systern as defined in claim 3, and wherein the said.

means connected between the grid elements comprises a pair of inductances arranged in intimate inductive relation, and capacity elements connected between corresponding ends of said inductances.

RICHARD H. SEAMAN. CARL A. SCHWENDEN. 

